Along with the development of nano-scale processes, e.g. nano electronics, nano materials, nanocarbon tubes, nano electric devices, and nano-scale analysis, the demand on the level of purity on ultrapure water and ultrapure gas will become more stringent. Taking the specification of ultrapure water as an example, a prediction on the trend of line width and water quality in nano electronic processes according to the International Technology Roadmap for Semiconductor (ITRS) stipulated by SEMATECH is listed in Table 1. The data listed in Table 1 show that the TOC, bacteria, fine particles, and ions contained in ultrapure water decrease along with a reduction in the process line width. Among which, the removal of organic matters (represented by TOC) in the purification of water is the most difficult to be overcome, because the removal of organic pollutants involves a conversion between two different phases, i.e. the pollutants can exist in a dissolved state or in a particle state. Meanwhile, the oxygen content and the metal content, etc. will influence the efficiency of organic pollutants removal. In a current ultrapure water system, major organic impurities removal units include a reverse osmosis unit and a TOC-UV unit. The ultrapure water system designed for a new process manufacturer, such as the 12-inch wafer manufacturer, mimics the design used in the 8-inch wafer manufacturer. Such a designed process mainly includes: a pre-treatment system including coagulation, sand filtration, a multiple filter, etc.; a primary treatment system including reverse osmosis, a vacuum degassing tower, an UV sterilizer, a mixed-bed deionization tower, a filter; and a polishing loop including a heat exchanger, an UV oxidizer, a polisher device, and an ultra-filter, etc. Said system includes only one loop, and the optimum TOC of the water generated can reach 1 ppb. Removal of the impurities in water mainly occurs in the pre-treatment and the primary treatment system stages. The polishing loop can further perform a minute removal on the remaining impurities in water mainly with the purpose of maintaining the quality of water. Since said systems according to the current technology can not further purify water, the present invention seeks a further development on a purifying system and method for further removal of minute organic matters in water.
TABLE 1Year20002003200520062007Technical node180 nm130 nm100 nm70 nm65 nmTOC (ppb)2<1<0.5<0.2<0.2
U.S. Pat. No. 6,579,445 B2 discloses a system for the production of ultrapure water having a specific resistance of at least 18.0 megohm.cm and a total organic carbon content of less than 1 ppb, that uses redox media, high energy catalytic activated carbon, ultraviolet radiation and high purity ion exchange media in series filtration. The system is designed to be fabricated on a sufficiently small scale to fit on a lab bench top.
U.S. patent published No. 2002/0134722A1 discloses an ultrapure water producing apparatus with reduced problems resulting from impurities generated after replacement of unit apparatuses. A TOC-UV, a CP and a UF membrane are provided in this order from the upstream side of a pure water supply route. Ultrapure water flowing through the UF film is supplied to a use point. A branch route branched from the pure water supply route is provided downstream of the UF film. A dissolved oxygen concentration meter is interposed in the branch route for measuring dissolved oxygen concentration in ultrapure water passed through the UF membrane. The branch route is connected to an oxidant decomposition unit. Oxidants included in ultrapure water flowing through the branch route are all converted into DO at the oxidant decomposition unit.
In a U.S. patent application Ser. No. 10/310,863, filed Dec. 6, 2002, the assignee of this application discloses a process and a system for processing waste water containing organic compounds, the disclosure of which is incorporated herein by reference. The system includes a UV/ozone oxidation removal module, or one or more removal modules connected in series whereas such a serial connection can be continuous or discontinuous. A UV/ozone oxidation module mainly includes an ozone generator, an ozone injector, an ozone dissolution tank, an ozone destructor, a UV reaction tank, a recycling pipeline. The efficiency of the UV/ozone oxidation removal module is controlled by the recycling ratio, the ozone concentration, and the intensity of UV light.